Generally, a capacitive microphone utilizes a capacitance between a pair of electrodes which are facing each other to generate an acoustic signal. A MEMS microphone includes a diaphragm being bendable and a back plate which is facing the diaphragm. The diaphragm can be a membrane structure to perceive an acoustic pressure to create a displacement.
In particular, when the acoustic pressure is applied to the diaphragm, the diaphragm may be bent toward the back plate due to the acoustic pressure. The displacement of the diaphragm can be perceived through a change of capacitance formed between the diaphragm and the back plate. As a result, an acoustic wave can be converted into an electrical signal for output.
The capacitive microphone can be manufactured by a semiconductor MEMS process such that the capacitive microphone has an ultra-small size. The diaphragm is spaced apart from a substrate to be freely bended upwardly or downwardly with responding to sound. The MEMS microphone has a plurality of anchors at end portions of the diaphragm. The anchors are spaced apart from each other along an end portion of the diaphragm. The anchors make contact with the substrate to stably support the diaphragm which is spaced apart from the substrate. The anchors are formed integrally with the diaphragm and are formed together in a process of forming the diaphragm.
Each of the anchors may have a cylindrical shape. The insulation layer located between the anchors may not be completely removed in a process of the MEMS microphone such that the insulation layer partially remains on the substrate. That is, a method of manufacturing the MEMS microphone includes a step of removing a portion of the insulation layer located between a diaphragm and a substrate, and a step of removing a sacrificial layer located between a diaphragm and a back plate to allow the diaphragm to freely move with responding to sound. In order to remove the insulation layer disposed under the diaphragm, an etchant may be provided to the insulation layer through a cavity formed in the substrate.
However, it may not be easy for the etchant to flow between the anchors and the interval between the anchors is also narrow such that the etchant may not reach the insulation layer. Thus, it may be not easy to completely remove the insulation layer located between the anchors. As a result, a portion of the insulation layer located between the anchors cannot be completely removed, and the remnant portion of the insulation layer may prevent the diaphragm from moving freely. Further, a buckling phenomenon in which the diaphragm cannot return to an initial position after being bent toward the back plate may occur to disturb the movement of sound wave.